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Don Kinzler, Published July 09 2010

Amur maple unlikely to damage or lift patio

Q: I am considering an amur maple near my slate patio because it would be nice to have a shaded area at the back of my house. I get high winds much of the year. What is the root system of the amur maple like? Do the roots grow horizontally or vertically? I am concerned that root growth might lift the slate. Is there a way to contain or control the roots without doing any damage?

If an amur is not the best tree for this application, what else would you recommend? (Maine)

A: They say to practice what you preach, so I do. I’ve got a beautiful amur maple next to our old concrete patio that provides beautiful shade, fall color and a playhouse for birds and squirrels. After 25 years of growth, we have had no surface root problems and no damage to our patio.

In a nutshell, go for it and enjoy.

Q: My red hot poker plant has done beautifully again this year and has doubled in size. Can I plant the seeds from the flowers or would I have to dig part of it up if I wanted to pass one on to my son? If both options work, can you give me some details? I haven’t found much information about this plant. (Lancaster, N.Y.)

A: This is a striking plant that is underutilized in most garden settings.

Dividing the rhizomes (underground stem) can be done in early fall. The seed can be collected and sown indoors during the winter months.

Q: Two weeks ago, I excavated soil from my backyard and placed it in my front yard. The soil is black clay and I want to plant grass in it. I’ve started by adding some peat moss to it, but I do not believe I have added nearly enough. I have been tilling it every few days to break up the large chunks. The soil is very wet and heavy due to the recent rains we’ve received. I have been contemplating purchasing a load of compost to mix in the soil if it would be of any benefit. Is there any advice you can provide on what else to do to condition the soil in preparation for grass seed? Does NDSU do soil testing? If so, how much soil does the lab need, where do I send it and is there a charge for this service? (West Fargo)

A: A load of compost and a load or two of sand would help. When you till, try to avoid doing it when the soil is too wet to be broken up. When it is ready to till, go in perpendicular directions. When you can get the texture to be similar to granola cereal, you have achieved your goal. The important thing to remember is to try to get the soil as homogenous as possible. This means no isolated clay, sand or peat/compost spots. When you get the soil to that point, send a sandwich bag full of the soil to the NDSU soil testing lab in Waldron Hall and ask for the standard testing. The charge is $26. Planting later in the season as you’ll be doing will be better because most of the weed seeds have germinated.

The soil and water also will be warmer to facilitate faster germination.

Q: I have a Tinkerbelle lilac that blooms but is a small plant. The lilac is about the same size as when we planted it six or seven years ago. Should it have reached its full size by now? I would like some advice on how to stimulate growth. (e-mail reference)

A: I had the same problem and eventually tore the lilacs out. They would flower, but not grow and looked punky, which is not wanted in any lilac plant. All I can do is give you the standard prescription for lilac care. Give the plant full sunlight as much as possible, fertilize with Miracle-Gro or something similar right after flowering and water it deeply during any extended drought period.

Check to see that it is not planted too deeply. Sorry I can’t give you better advice. One of my readers may have a better answer. If so, I’ll pass it on to you.

Q: I have a spiral juniper that is starting to turn brown. I have had it for four years and always has looked very nice. I put fertilizer stakes in the ground each spring, but this year something is going wrong. Can you please help with any suggestions? (e-mail reference)

A: I’m sorry to tell you that you have wasted your time and money in messing around with fertilizer stakes. As for the discoloration of the foliage, there are many possible causes. I suggest contacting your county Extension agent to see if there is someone who can assist you. Go to http://www.csrees.usda.gov/Extension to find a local contact.

Q: We have nine mature cottonwood trees that are around 100 years old. We are digging out a garden near one and encountered a large bundle of roots. We are not going to cut the roots because we value these trees. If we remove the heavy clay soil from under the trees so that our shorter-rooted herbs have access to fluffier soil, will we damage the tree? Should we just leave that strip of soil in place and work the bed on either side of the roots or is it OK to plant herbs over the top of the cottonwood roots? (e-mail reference)

A: A simple planting of herbs will not hurt these stately cottonwoods. If you can work up the soil with a small tiller between the major roots, the herbs will have a better chance of getting established.

Q: Why will asparagus grow wild in a ditch, but I can’t get it to grow in my garden? Five or six years ago, I planted 15 plants, but only seven survived. The following spring, only four survived. By last year, only one of the original plants was still living. This plant has three or four spears this year and all of the seedlings are sparse. I have fairly sandy soil and I thought maybe it was too dry in the spring, but this year was plenty wet until the remaining plant started to sprout. I have harvested very little. What am I doing wrong? Should I try mulch? Thanks for any suggestion. (Barnesville, Minn.)

A: Never look for justice when working with Mother Nature because she is neutral to our emotions, wishes and desires. If it makes you feel any better, it took me a couple of tries to become a successful asparagus grower, so I’ve experienced the same frustrations you have. I’ve just revised our publication on growing asparagus and rhubarb. To read it, go to http://www.ag.ndsu.edu/pubs/plantsci/hortcrop/h61.pdf. My establishment success came from using Jersey Giant and Jersey Centennial. Keep in mind they need full sun.

Q: This is not going to be a good year for chokecherries. Many of the cherries I do have hanging on my trees have an infestation that I’ve seen many times through the years. There are no stones developing in the cherries, but there are several tiny, orange worms inside. The cherries that are infested are somewhat yellowish and swollen. In the past, I have blasted the tree with a systemic pesticide. I’m not sure if I accomplished anything because I don’t know what happens to the worms. Is this the beginning of the tent caterpillar cycle or is this the larva of a moth? I would get more excited if there was a good crop. (e-mail reference)

A: Spraying now will do very little, so don’t bother. This fall, pick up all the fallen fruit and anything else that remains. Next spring, spray dormant oil and then, as the blossoms start to drop, spray with Sevin or Malathion insecticide.

Repeat the spraying in 10 days. That should take care of most of these pests.

Systemics will not work fast enough.

Q: My lawn is turning yellow. Is it because the lawn lacks iron? What product can one use to bring back the natural color? I fertilized the first of last month. (Portland, N.D.)

A: See if you can get an ironized lawn fertilizer. It has from 3 to 5 percent iron. If that doesn’t change things, then it is something else and I would need a photo or sample.

Q: I am not a green thumb gardener by any means, but I know I want a pink flowering dogwood in my front yard. When we went to the nursery, none of the dogwoods were flowering. However, the worker said the tree I picked would have pink flowers. They came and planted it for us. About two weeks later, a few white flowers appeared. When we called the nursery, they told us that sometimes transplant shock will cause the flowers to revert to white but should grow pink next year. Is this true? (Pennsylvania)

A: Oh, the lies people tell! Shame on the person who told you that. They just don’t want to replace the tree. Are you sure the flowers (bracts) didn’t open with a blush of pink and fade to white? Did you get a cultivar name? There are more flowering dogwood cultivars than the name Smith in the New York City phone directory! If there was no tag with the cultivar’s name, such as Cornus florida var.rubra, Andre or spring song, then you were taking a roll of the dice as to what it was you were getting. The person at the nursery wants you to think that once pink or red flowers show up, they always will be that color. Nice try, but it doesn’t work. If they claim it does, then I have to be shown.

Q: We sprayed our apple tree for worms that get inside the apples. We used a fruit tree spray with bonide that was supposed to be sprayed on early in the spring and again after the tree bloomed. Well, it never got any blossoms. We also sprayed a neighbor’s apple tree for the same problem and it never bloomed, either. Could it have been the spray that caused them not to bloom? Thanks for your help and I always read your column. (Gackle, N.D.)

A: No, the spray would not have prevented the trees from blooming. It might have caused it to not set fruit, but it wouldn’t have caused it to not bloom. Very likely our winter weather this year nailed the blooms. Next year, wait until the blooms are fully open and just starting to drop their petals before spraying.

Repeat again in 10 to 12 days.

Q: I have two houseplants with mold problems. One has yellowish mold, while the other has whitish mold in the soil. Both plants seem healthy and neither seems to have mold on the plant. I thought I’d killed off the yellow mold awhile back by letting the plant dry almost completely (it’s a tough little hoya). I repotted it last year, and the mold returned with a vengeance. Can you recommend a good fungicide to put in the soil of these plants? I worry the mold may spread to my African violets. (e-mail reference)

A: This is a saprophyte problem, not a parasite. It is working on digesting the organic matter in the potting soil. This is nothing to worry about from the plant’s point of view. If you are concerned, repot the plants again using a new or clean pot and heat your potting soil in a microwave for about four minutes to pasteurize everything that is in the media.

Q: I have a large eastern cottonwood in my backyard. I love this tree because it provides a lot of shade for my house. About two months ago, big pieces of bark started falling off the upper branches. Some branches are pretty big. I called a local tree and turf adviser who said the tree had borers and larvae. He recommended removing the tree and nothing else. About half the tree is still alive. I would like to save the tree, so is there any way to spray for this problem? If the tree is removed, will these borers move to my other cottonwood and pine trees? (e-mail reference)

A: A half-dead tree is not something you want to try to save, especially one that is infested with borer larvae. Get the tree removed as soon as possible by a qualified, insured and bonded tree expert. At the same time, have the surrounding trees checked for insect infestations so that remedial action can be taken before it gets too late as it is with your cottonwood tree. I wouldn’t waste any time. I don’t mean to scare you, but the possibility of a large tree falling and damaging your house or a loved one isn’t worth debating.

Q: I purchased and planted two blue spruce trees. While they were being loaded at the store, the very top branch that sticks straight up broke off one of the trees. I didn’t think much of it at the time, but now am worried that the top vertical branch might be responsible for the tree’s growth. I’m not a tree expert, so I could be wrong about how the tree will grow taller. Without the center vertical branch, will my tree have stunted growth? The tree also was oozing a little sap where the top branch broke off. To protect it from insects, I put some tape on it. Should I leave it exposed to dry up and heal? (e-mail reference)

A: First, get the tape off the tree and then stop worrying about the future of the tree. One of the lateral branches, probably the longest one, will curve up and become the central leader with only a little crook in the stem to show for it. In time, the little crook will not be as noticeable. Sap flow in all living trees is normal at this time of year, so don’t worry about that.

Q: I live in the Niagara region of Ontario, Canada. I had purchased thuja whipcord last spring. I had not decided on a permanent location for this evergreen, so I kept it in a large container. Close to winter, I made sure the soil was dry and put the container in my sun porch. During a warm spell in March, I brought it outside where it was exposed to several mornings of frost.

What looked to be a successful winterization quickly turned the thuja into a dry and browning shrub. I really love this plant, so its there a chance that it will survive? I now fertilize it every two weeks. (e-mail reference)

A: The mistakes you made in judgment about the right things to do, such as allowing the soil to dry and bringing it indoors, is what killed the tree. It would have been a better choice, since you were uncertain as to where to plant the tree, for you to plunge the pot into the soil and give it a good soaking before the winter freeze took place. A hydrated plant has a much better chance of surviving low temperatures and wind stress than one that is lacking in sufficient water in the cell tissue. I’m afraid that you are wasting your time watering and fertilizing it. You are better off throwing this one out and getting another one once you have decided where to plant it.

Q: I have a ficus hedge that has about a 5 percent leaf infestation by a dark, crawling insect. It lays tiny white eggs enclosed by a leaf. Can you tell me the insect and what form of insecticide would reach this pest? My gardener said he has sprayed twice, but there was no improvement. (e-mail reference)

A: You need a systemic insecticide to control whatever this pest is. Look for a product that contains the active ingredient Imidacloprid. Bayer has a product on the market known as “Bayer Advanced Tree and Shrub Insect Control.” There are other brands that carry the same ingredient if the Bayer product is not available where you shop.

To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail ronald.smith@ndsu.edu.